Does it have the double capacity accelerator pump? That was the problem it would reduce to the normal /half volume once it warmed to remp. If you left it disconnected you would have the incorrect pump shot.

Those idle mixture caps can be removed. It means its likey someone was adjusting it.

They work awesome on a driven vehicle. They can make as much power as any other carb of its size. Not like a holley is going to make more power just cause it is a holley. That is superstition and brand loyalty I havent got time for.